[#RSRP-42842] Gives bad advice: "Parameter can be of type System.ICloneable"

ReSharper

Gives bad advice: "Parameter can be of type System.ICloneable"

Created: 10 Jun 07 19:44 Updated: 11 Jun 07 20:33

Component/s:

Code Analysis

Fix Version/s:

Mirabilie Futurum

Security Level:

Everybody (All jira users)

Original Estimate:

Unknown

Remaining Estimate:

Unknown

Time Spent:

Unknown

Build:

448

Description

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(build 3.0.448.7)

I believe I can guess why it thinks so, but in this case it would not be good programming style to change the parameter to ICloneable, because anything but a Cow will make the routine fail. I think R# needs some more sophisticated analysis to understand that the input argument is basically constrained to being a Cow.

using System;

namespace ConsoleApplication1 {
  public class Program {
    public static void Main(string[] args) {
      Cow c1=new Cow();
      Cow c2=c1.CopyCow(c1);
    }

    private class Cow : ICloneable {
      public object Clone() {
        return this.MemberwiseClone();
      }

      public Cow CopyCow(Cow other) { //R# says: "Parameter can be of type System.ICloneable"
        return (Cow)other.Clone();
      }
    }
  }
}

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Vladimir Reshetnikov - 10 Jun 07 21:56

I would recommend to use the following approach:

public T Copy<T>(T other) where T : ICloneable // No warnings here
{
    return (T) other.Clone();
}

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Corey Kosak - 10 Jun 07 22:32

It is possible my example was poorly chosen. Usually when I provide examples to you I try to create something as simple as possible that illustrates the problem.

There are always ways to work around a problem. Likewise there are always ways to get ReSharper to stop warning about something. This does not mean that ReSharper's warnings are always valid.

Here is another version of the code. I think that it is the best way to write it. If you are saying I should write longer code just to get ReSharper to stop warning about ICloneable, I would have to disagree.

using System;
using System.Collections;

namespace ConsoleApplication1 {
  public class MyClass {
    private readonly Hashtable ht;
    private readonly OperatingSystem os;

    public MyClass(Hashtable ht, OperatingSystem os) {
      this.ht=(Hashtable)ht.Clone();
      this.os=(OperatingSystem)os.Clone();
    }
  }
}

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Eugene Pasynkov - 11 Jun 07 20:33

Right now, I do not know what to do with this request.
On suggesting parameter type, except code analysis, we do some simple heuristics.
This example shows that they are not enough